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amplified, then rectified by diode D4. The rectified DC level is
input to pin 3 of IC14 and amplified to be output from pin 1. (DC
output can be chosen according to the loudness of voice input.)
The output from pin 1 is supplied to pin 42 of CPU (IC17), and
read by A/D converter to become the trigger of transmission.
2. The output from pin 6 of IC11 is supplied to pin 1 of IC13 and
amplified then output to pin 6 through the splatter filter.
3. Also in IC13, the tone generator circuit outputs CTCSS signal (60
~ 250 Hz) from pin 16 continuously corresponding to programmed
CODE. These signals are added at the amplifier input pin 5 and
output from pin 4.
4. The output from pin 4 of IC13 is supplied to RF block passing
through connector CN4 and CN5.
20.3. Other operation
LCD:
LCD on CPU board consists of 2 common terminals (pin 18, 19) and 17 segment terminals (pin 1
~ 17), and it is driven by CPU directly using the method of 1/2 duty dynamic lighting.
EEPROM:
EEPROM on CPU board is connected to CPU directly with the serial signal, all kinds of setting
items are reserved. The default setting and the change of the settings in daily use are always
reserved.
CPU:
8 bit/chip built-in ROM type-CPU are employed, LCD direct drive, built-in A/D convertor and
serial port are provided.
X2:
The crystal oscillator of 3.6864 MHz on CPU board, which is used as CPU clock, the reference
for CTCSS (tone signal) and for the generation of the reference frequency of scramble process.
The required accuracy by CTCSS is 1/250=0.4%. The crystal is 50 ppm.
RESET IC:
IC15 on CPU board is the RESET IC, which resets the CPU when the battery voltage becomes
2V or below. On the contrary, when the voltage is more than 2V, it releases the RESET mode
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